Conventionally, a two-dimensional light scanning apparatus has been known, which has a MEMS (Micro Electro Mechanical System) mirror driving at a high speed while irradiated with laser light. In order to perform drawing with this two-dimensional light scanning apparatus, a MEMS mirror may drive at its resonance frequency in both vertical and horizontal directions for scanning as drawing Lissajous figures. In this case, drawing positions can be separated into horizontal positions X as horizontal components and vertical positions Y as vertical components. A horizontal position X is represented by the following equation 1, where the horizontal frequency is a [Hz] and the time is T [sec]. Meanwhile, a vertical position Y is represented by the following equation 2, where the vertical frequency is b [Hz], the time is T [sec], and the phase with respect to X is φ.X=sin(2π·a·T)  Equation 1Y=sin(2π·b·T+φ)  Equation 2Here, for example, in a case of scanning one frame while T varies from 0 to 1, scanning trajectories are represented as FIG. 3(a) in which all the trajectories do not overlap with each other, where a=51, b=10 and φ=0.
However, the resonance frequency of a MEMS mirror and so forth may vary due to conditions such as temperature and secular change. For example, if the value of “a” varies from 51 to 52, each two scanning trajectories overlaps to trace the same trajectory, so that a distance between each trajectories in the vertical direction broadens as shown in FIG. 3(b). In addition, when the phase φ varies from 0 to ¼π [rad], drawing trajectories are represented such that distances between drawing trajectories are uneven as shown in FIG. 3(c), even under the condition of a=51 and b=10.
Therefore, as disclosed, for example, in Patent Literature 1 (claim 5 and paragraph 0021), a configuration is possible that has a scanning line detecting means and a control means. With respect to two at least neighboring scanning lines among a plurality of scanning lines, the scanning line detecting means can detect the distance between them in the sub-scanning direction (vertical direction) and the direction of main scanning (horizontal scanning), and the control means controls the phase of the angle of deflection of a deflector (MEMS mirror) such that the distance between two at least neighboring scanning lines detected by the scanning line detecting means is fixed in the sub-scanning direction, and the directions of the main scanning are opposite one another.